SQL ANY和SOME关键字是否在所有SQL方言中都是同义词? [英] Are SQL ANY and SOME keywords synonyms in all SQL dialects?
问题描述
在Postgres中，当在谓词表达式的右侧使用时，ANY和SOME是同义词.例如，它们是相同的:
In Postgres, ANY and SOME are synonyms when used on the right hand side of a predicate expression. For example, these are the same:
column = ANY (SELECT ...)
column = SOME (SELECT ...)
在此处记录:
http://www .postgresql.org/docs/9.1/static/functions-subquery.html#FUNCTIONS-SUBQUERY-ANY-SOME
我观察到ANY和SOME至少受以下SQL DBMS支持:
I have observed ANY and SOME to be supported by at least these SQL DBMSs:
- DB2
- 德比
- H2
- HSQLDB
- Ingres
- MySQL
- Oracle
- Postgres
- SQL Server
- Sybase ASE
- Sybase SQL Anywhere
- DB2
- Derby
- H2
- HSQLDB
- Ingres
- MySQL
- Oracle
- Postgres
- SQL Server
- Sybase ASE
- Sybase SQL Anywhere
我是否可以安全地假设所有这些方言(以及其他方言)都将ANY和SOME视为同义词，或者在任何/某些DBMS中这两个关键字之间是否存在细微差别?
Can I safely assume that all of those dialects (and others, too) treat ANY and SOME as synonyms or is there a subtle difference between the two keywords in any/some DBMS?
我在SQL92定义中发现了这一点:
I have found this in the SQL92 definition:
<quantifier> ::= <all> | <some>
<all> ::= ALL
<some> ::= SOME | ANY
这没有说明ANY和SOME的语义.在文档的后面，仅引用<some>，而不引用两个关键字.我怀疑至少在某些DBMS中NULL处理可能存在细微差别.欢迎任何/某些指向明确声明的指针，无论是否可以假设.
This doesn't say anything about the semantics of ANY and SOME. Later on in the document, only <some> is referenced, not the two keywords. I'm suspecting that there might be a subtle difference in NULL handling, for instance, at least in some DBMSs. Any/some pointer to a clear statement whether this can be assumed or not is welcome.
推荐答案
引用后几行，SQL92标准还指定了<some>的语义，即:
Few lines after what you're quoting, the SQL92 standard also specifies the semantics for <some>, namely:
c) If the implied <comparison predicate> is true for at least
one row RT in T, then "R <comp op> <some> T" is true.
d) If T is empty or if the implied <comparison predicate> is
false for every row RT in T, then "R <comp op> <some> T" is
false.
e) If "R <comp op> <quantifier> T" is neither true nor false,
then it is unknown.
这些规则适用于<some>令牌，而与它是SOME还是ANY替代方案无关，所以是的，根据标准它们是同义词
These rules apply for the <some> token, independent on whether it is the SOME or ANY alternative, so yes, they are synonyms according to the standard
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